LEDs are used in various fields such as numeral/character display elements, signal lights, light sources for lighting, and display devices. An LED as a light source may include a holder, a substrate located at one end of the holder, and a plurality of LEDs arranged on a flat plane of the substrate. Since the LEDs generate heat when working, the substrate needs to dissipate the heat generated. However, the size of the LED may limit the size of the substrate, thereby limiting a heat-dissipation efficiency. Therefore, there is room for improvement within the art.